Resaw primer - with a kataba rip saw


Here is a short episode about resawing boards into thinner boards. In this case I tried my hand at a 3/4" x 14" x 24" piece of reclaimed Port Orford cedar.  The saw was a 300mm rip kataba. Turns out I could have used a larger one.




Since it was recycled lumber I used an expendable plane to shave off the embedded grit and damage. Then I planed one face flat (an aromatic joy) and planed the long edges square. Next I scribed (kebiki) the max thickness line on all 4 edges and planed face 2 to that line. I knew that I may not get a second chance to plane the faces once the cut was finished due to possible stress relief and deformation of the thin boards so I made sure I had two flat, parallel, planed faces before starting the resaw cut. On edges and ends I scribed a line at a half kerf's distance from the center line (to center the kerf basically). 

The board was wide and I do not have a vise, so it had to be stood on a long edge and clamped to a rigid vertical surface. I have a heavy scrap wood horse that works well. Since the faces were ready for final planing, deep gouges or scratches were to be avoided - so clamping was done with soft pine blocks and minimal pressure. Any surface coming in contact with POC had to be clean and flat. Don't allow sawdust to fall down into any gap between your vertical surface and the board - even if you have to tape on paper or plastic to divert the dust. You can skip this precaution if the board is to be surfaced later.

keeping chips from falling in and damaging planed surface
 As cutting progressed, I flipped the board from edge to edge to hold the scribe line and get around the fact that the saw blade was not as long as the board was wide. Work the 4 corners first to establish accurate kerfs on all edges and ends. Cut past the half way mark on the ends and edges so you can reach the kerf from the adjacent corners. Then tackle the uncut diamond-shaped area in the center of the board. 

Cut from ends toward middle. Pull the saw into the grain.

Ideally you have a saw long enough to protrude from both sides of the board or at least well past the midpoint to make tracking easier. Otherwise, you will be cutting blindly on this last part and your cuts may drift and bypass each other. How do I know this? Anyway, it is critical that the 4 corner kerfs you started are coplanar before you go extending them. Kataba style rip saws have a lot of clearance. If you feel the blade binding or resisting on the push stroke, it is probably bending in a curved kerf. Don't push hard on the saw as you stroke or you may deform the blade and make a curved kerf. Let the saw do the work. Light pressure.

Clamping during cutting requires a wide shim the thickness of your kerf so you can clamp the cut area without splitting the board. Best to use a wood shim in case you saw into it.  

A couple hours later you will have two thinner pieces of wood, a dusty workspace, and no further romantic ideas of hand resawing wide boards any time soon. You will also know just how well sharpened your saw is. 

In my case the two new (thinner) pieces are no longer flat on either side because of the relieved stress. Let it set a few days so the moisture can normalize, but you may not be able to flatten them. If it has to be perfectly flat, cut it from the middle of the board from the start. But that is 2 cuts, not just one. And maybe that will warp, too.

Next scribe the max thickness you can get from each half onto all the edges of each board. Plane to that scribe line carefully. You want the panels to be consistent thicknesses. These panels cupped a lot. If the panel is thin and to be framed on 4 sides you should be OK, it just increases the likelihood of the panel splitting or distortion of your frame. Here is where one of the pieces ended up.




Comments

Adam Weil said…
Very nicely done! I've always wondered how to split a board of substantial width with a basic handtool set, and this definitely does the trick. But only with a lot of patients and a sharp saw.

Do you think the tape & plastic was over kill since you had to replane the surfaces to reflatten them?
Peter Mac said…
For sure it was overkill but in the end I did not re-plane the surface because it remained in good shape. Just part of the process of keeping bruising, dings, and scratches to a minimum.
David Wong said…
Very informative blog. Thanks for posting these projects and techniques. English language information on japanese tools and methods is so scarce. I just discovered your blog while doing a search for "andon".